Luminosity Functions and Point Source Properties from Multiple Chandra
Observations of M81

Abstract

We present an analysis of 15 Chandra observations of the nearby spiral galaxy
M81 taken over the course of six weeks in May--July 2005. Each observation
reaches a sensitivity of ~10^37 erg/s. With these observations and one previous
deeper Chandra observation, we compile a master source list of 265 point
sources, extract and fit their spectra, and differentiate basic populations of
sources through their colors. We also carry out variability analyses of
individual point sources and of X-ray luminosity functions in multiple regions
of M81 on timescales of days, months, and years. We find that, despite
measuring significant variability in a considerable fraction of sources,
snapshot observations provide a consistent determination of the X-ray
luminosity function of M81. We also fit the X-ray luminosity functions for
multiple regions of M81 and, using common parametrizations, compare these
luminosity functions to those of two other spiral galaxies, M31 and the Milky
Way.Comment: 20 pages, 11 figures to be published in Ap